Nonstaining rubber

ABSTRACT

A rubber composition is provided having nonstaining property containing therein 5-50 PHR of a novel nonstaining aromatic hydrocarbon process oil comprising polypropylnaphthalene. The process oil comprises polypropylnaphthalene of the general formula:   WHEREIN R is propyl group, n is an integer of 2 to 4, R&#39;&#39; is a hydrogen atom or a methyl group and n&#39;&#39; is an integer of 0 to 2, the total number of carbon atoms in the alkyl side chains being six to 13, and has an aniline point of not more than 10*C. It is suitable for the uses of light color rubber compositions with no staining and bleeding.

United States Patent [191 Takahashi et al.

1 July 29,1975

1 1 NONSTAINING RUBBER [75] Inventors: Masaaki Takahashi, Tokyo; NoboruIshizawa, Hyogo; Masazo Nishida, Osaka, all of Japan [73] Assignees: TheToyo Rubber Industry Co.,

Ltd., Osaka; Kureha Kagaku Kogyo Kabushiki Kaisha, Tokyo, both of Japan;part interest to each 22 Filed: Jan. 4, 1974 [21] Appl.No.:430,852

Related U.S. Application Data [63] Continuation-in-part of Ser. No.153,047, June 14,

1971, abandoned.

[30] Foreign Application Priority Data June 12, 1970 Japan 45-51196 [52]U.S. Cl 260/5; 208/14; 260/33.6 AQ; 260/668 R [51] Int. Cl C07c 15/24;C08c 11/22 [58] Field of Search 260/33.6 AQ, 668, 5; 208/14 [56]References Cited UNITED STATES PATENTS 8/l972 Mills et al. 260/33.6 AQ

OTHER PUBLICATIONS Kirk-Othmer Encyclopedia of Chemical Techn."

(2nd Ed.) (Vol. 14) (Interscience) (N.Y.) (1967), pages 849-850, 853,854. TP9E68.

White et al., Rubber Journal, pages 50-52 and 55 (June 1966).

Primary ExaminerDonald E. Czaja Assistant ExaminerH. H. FletcherAttorney, Agent, or Firm-Sughrue, Rothwell, Mion. Zinn & Macpeak [57]ABSTRACT A rubber composition is provided having nonstaining propertycontaining therein 5-50 PHR of a novel nonstaining aromatic hydrocarbonprocess oil comprising polypropylnaphthalene.

The process oil comprises polypropylnaphthalene of the general formula:

lee

11 Claims, No Drawings l NONSTAINING RUBBER CROSS REFERENCE TO RELATEDAPPLICATIONS The application is a continuation-in-part application ofcopending application, Ser. No. 153,047, filedtlune 14, 1971, nowabandoned.

BACKGROUND OF THE INVENTION plasticization effect and reduction in cost.Particularly,

and the lower the aniline point is the more increased is the stainingproperty. g I

Thus, the rubber composition with which the present invention isconcerned may be suitably used. as for ex ample, for light color rubbercompositions for white ribbons of tires, or black color rubbercompositions in contact with light color rubber compositions.The-compositions also have application in fields where rubbercompositions compounded with a large amount of a softening agent havebeen believed not to be desirable. for example, in tirecarcasses, canvasshoe soles, etc. Further, it is greatly expected that the rubbercompositionof this invention will be applied in new fields, suchascolored. tires or patterned tires. 7

DETAILED DESCRIPTION OF THE INVENTION 200 to 250C fraction) obtainedfrom a raw material a large amount extending from to 50 partsby weight,per 100 parts by weight of rubber, of petroleum oil softening agent hasbeen employed for styrenebutadiene copolymers of solution-polymerizedpolybutadiene.

Most of the petroleum oils which have hitherto been employed areso-called aromatic extender oils,,which may be advantageously compoundedin a rubber composition in a large amount, but impart staining and lightdiscoloring to a rubber composition.

On the other hand, naphthenic extender oils have also been employed, asless or nonstaining softening agents in rubber compositions.

The compounding amount of naphthenic oil was however, fairly limitedbecause the compounds are likely to bleed on a surface of the rubbercomposition when they are used in large amounts which leads to stainingof rubber. US. Pat. No. 3,681,279 discloses an attempt in thepreparation of'a nonstaning oil byelimi-' arom atization for eliminatingpolar compounds. Therefore, the product according to the process'of thispatent contains 1555% non-aromatic hydrocarbons, i.'e., sat

urated hydrocarbons. Thus, there 'is 'no'disclostire therein withrespect to the fact that 100% aromatic compound is useful to achievenonstaining properties.

The present invention has been accomplishedf to solve the prior artdefects or drawbacks, as above, in

softening agents for rubber. I

SUMMARY OF THE- INVENTION According to the invention, thereis' 'thusprovided a rubber composition containing therein a novel aro matichydrocarbon process oil comprising polypropylnaphthalene, which oil hasan aniline point of not more than 10C, preferably not more than 5C andexhibits no staining property when compounded with a rubber composition.

This finding is unexpected in view of conventional ideas or knowledgethatusual aromatic oilscurrently used have aniline points'ih 'a ran geof from 25 to 40C:

for l to 0001 second, a naphthalene fraction separated from coal tar, anaphthalene fraction in a by-produced bottom oil obtained in thecatalytic improvement of n h hw A The above process oil comprisingpolypropylnaphthalene obtained in the present invention is quitediffercnt fro m", the conventional process oil generally obtainedthe'purifi'cation and separation of a mineral oil, That is, the processoil of the present invention contains no carbon'bonding constitutinganaphthene ring,- and is anoil fraction composed of purearomatichydrocarbons. Therefore, the conventional. manner foranalyz ingthe component (such -as-n -d"-M method, V, .G.C. method, which arecalculated from the 'measurement'of physical'constants) is not applied,and it was confirmed by gas chromatography, NMR, mass-spectrum, etc.,that the process oil comprises a naphthalene compound a having two tofour propyl groups; such as, dipropyl-i naphthalene,tetrapropylnaphthalen'e, etc.

Isomers thereof are of course in'c-luded, but in.,the' present inventionit is not necessary to separate the isomers.-Any compounds'representedby the'above general formula having a boiling point-range of 280 to-450C can beemployed. The reason for specifying the general formula ofthe compounds according to-the present, invention is based on theconsiderations of methylnaphthalene and 'dimethylnaphthalene" 1containediin a naphthalene fraction, and even though those; propylcompounds are contained. in the process oil-,.-. there is ,no problemin'practicing. the ,present inventionwt,

The physical propertiesof polypropylnaphthalene oil 1 of the presentinvention are generally as'fo'llows.

Boiling Point 3 0 400c Cminucd diffusing towards the surface of therubber composition u g s article. Also the rubber compositions are notat all de- Roflccumcc 8 graded in mechanical properties, such as,tensile Flash Point 100C strength.

. h C 5 Moreover, it should be remarked that the rubber Pmm um I mcomposition or compound has good processability, for ybolt example,tackiness and adhesiveness.

000B In particular, the use of the rubber composition is eflective forthe improvement in adhesion to polyester, Aniline Point not more thanl0(, nvlon or Steel cord prclcrahl not more I than 5( lt was generallyrequired that various light color or white rubber articles, for examplewhite ribbons for Table l given below shows the performance on onetires, not only do not stain, but also can maintain their of the processoils employed in the examples of the whiteness from the viewpoint ofcommercial value, present invention, as compared with those of typicalwhereas it has been a general tendency in recently that process oils nowcommercially available. a large amount of a process oil is compoundedwith TABLE 1 Performances of Various Process Oils Process OilConventional Conventional Conventional Article Paraffinic NaphthenicAromatic of the Item Oil Oil Oil Invention Specific Gravity 0.87350.8859 1.0065 0.9677 (d Aniline point 997 70.0 34.1 10.0 (C.)

Reflectance 1.4794 1.5068 l.57l5 1.5654 (Nll'lfl) Color (ASTMD-ISOO)l.() 3,7 3.0 l.()

VGC 0.805 01:78; 0.9561 1.082

Remark VGC (Viscosity gravity constant) 0755 In the above equation, Gsymbolizes the specific gravity at 60F. and V symbolizes the Sayboltuniversal viscosity at 2l0F.

As is apparent from Table 1 above, the process oil for use in thepresent invention is characterized in that its aniline point is fairlylow with high aromaticity.

The rubber component, with which the process oil for use in the presentinvention having the above mentioned good properties may be compounded,includes any kind of elastic high polymers, such as, natural rubbers orsynthetic rubbers. The synthetic rubbers are exemplified bystyrene-butadiene copolymers obtained by emulsion polymerization,butadiene-acrylonitrile copolymers. polybutadiene, styrene-butadienecopolymers, obtained by solution polymerization. polybutadiene,neoprene, polyisoprene, styrene-butadiene copolymers, orbutadiene-acrylonitrile copolymers. prepared by alfin catalystpolymerization.

In particular, polymers having high polarity and great cohesive energybetween. main chains. for example styrene-butadiene copolymer,butadiene-acrylonitrile copolymer, or neoprene have strong affinity forand swell readily in the process oil of the present invention so that itis possible to incorporate the process oil in the polymer in a largeramount.

The rubber compositions containing the specified process oil to whichthe present invention relates is nonstaining and bleeding or bloomingphenomena do not tend to be caused by the process oil migrating ofrubber in rubber compounding, which tendency often leads to rubberstaining due to the large amount of the process oil.

In accordance with the invention, such requirement as above can besatisfied by the use of the process oil specified hereinbefore.

Thus, the rubber compound containing the particular process oil of theinvention is characterized in that there is no danger that the oileither discolors a light colored compound or transfers from a blackrubber compound to a light colored or white compound adjacent thereto,and, as a result, discolors the latter.

In other words, the process oil for use in the invention hassubstantially no bleeding nor blooming tendency and can keep a clearcolor.

The compounding amount of the process oil for proving the rubbercompound of the present invention is suitably in a range of from 5 to 50PHR. When the amount is less than 5 PHR, the inherent effect of theprocess oil on the rubber, i.e., improving processability, cannot bedeveloped, while when the amount is in excess of 50 PHR, an adverseinfluence may be exerted upon the properties of the rubber itself.

In compounding operations, other usual ingredients of the rubberindustry may also be incorporated as desired. Further the process oil ofthe invention may be used in combination with a minor proportion of acommercially available process oil.

The preparation of the rubber composition of the present invention maybe accomplished, forexample, by a procedure of producing a so-calledoil-extended rubber which comprises mixing the specified process oil inemulsified form with a copolymer rubberlatex. coaqulating the mixture bya salt or acid and drying the resultant rubber composition. or by anorthodox procedure by means of a mixing apparatus. such as a Banburymixer or open mill. 1n the former procedure. it may be advantageous tofurther add carbon black on extending the rubber with oil to prepare amasterbatch rubber. It is to be understood that any procedure forpreparing a rubber composition may be conducted.

The following examples in which, unless otherwise stated, and parts areboth by weight. will illustrate the embodiments of the invention in moredetail.

EXAMPLE 1 A polymer having a Mooney viscosity of 120 was prepared by thepolymerization of 72% butadiene with 28% styrene at 5F using a 5% potashsoap solution as emulsifier so that convention rate is 75%. To theresulting polymer latex was added and mixed thoroughlypolypropylnaphthalene in an emulsified form, which polypropylnaphthalenehad been prepared by cracking a petroleum oil hydrocarbon at a hightemperature of l,O0OC to yield a naphthalene fraction having a boilingpoint range of 200 to 250C, hydrotreating the distillate in the presenceof a cobaltmolybdenum catalyst and concurrently purifying it, andreacting the hydrotreated product with propylene in the presence ofasilica-aluminum catalyst. The process oil is mainly composed oftripropylnaphthalene having a boiling point range extending from 330 to380C and an aniline point of 8C, and is hereinafter abbreviated as AX-lHere, an emulsifier comprising 2 parts of oleinic acid and 2 parts ofammonium hydroxide per 100 parts of the process oil was used for thecmulsification of the oil.

The mixture so prepared was flocculated by a salt or acid to obtain aproduct in small particle form, which product was then dried, milled onan open roll mill and formed into a thick sheet by a sheeting step. Thethus obtained product comprised of the mixture is hereinafterabbreviated as PAX." The mixture PAX" comprises 100 parts of the polymerand 37.5 parts of the process oil and has a Mooney viscosity value of55.

By way of comparison. a commercially available napthenic oil-extendedrubber, as shown in Table 2 below, was employed as the rubber component.The thus prepared mixture PAX" (this invention) and the commerciallyavailable naphthenic oil-extended rubber (comparative) were compoundedand mixed respec tively with the ingredients listed in compoundingformulae of Table 2, i.e., in accordance with Compound No. 11 for theformer and Compound No. l for the latter by means of Banbury mixer inwhich the process oil for use in the present invention (Abbr. AX-l) forthe former and a commercially available naphthenic process oil (Abbr.NA) for the latter were employed respectively as softening agents. Thus,both rubber compounds were prepared. The various properties of therubber composition, uncured, and cured, obtained in accordance with thepresent invention are shown in Table 3 and Table 4 in contradistinctionto those of the comparative composition.

Oil-extended rubber having a Mooney viscosity value of 100C. (ML of 48composed of a st'yrene-butadienc copolymcr rubber with a styrene contentof 23.5% and 37.5 PHR of a nonstaining naphthenic process oil.

Natural Rubber Smoked Sheet No. 3.

Fast Extrusion Furnace Carbon Black Polyolefin Tackificr NA is anaphthenic process oil Sonic R-50" and AX-l is the polypropylnaphthaleneof this invention.

Styrenated phenol N-cyclohexyl-Z-benzothiazolesulphenamide TABLE 3Properties of (ireen Sheet 1 I Compound 1 Compound ll (Comparative)(This Invention) Mooney viscosity 25 26.5 (ML at 100C.)

Mooney scorch time unit rise time at 125C.) 15" 430 Strength (Kg/em")(23C.) 1.21 1.28 (speed; mm/min) (40C.) 0.52 0.85

Tackiness (Kg) (23C.) 2.32 2.01 (speed by Pick-up method: 1000 mm/min)(40C.) 1.1 1.78

TABLE 4 Properties o1 Vuleanizate* *The vulcanizate was obtained under apress vulcanization condition of 150C. for 40 minutes from the greencounterpart.

A process oil was prepared by cracking crude oil at a temperature of1,200C. to yield a naphthalene fraction having a boiling point range of200 to 250C. hydrotreating the distillate in the presence of acobaltmolybdenum catalyst and reacting the hydrotrcated product withpropylene in the presence of silicaaluminum catalyst. The thus-obtainedprocess oil is of polypropylnapthlene mainly composed oftripropylnaphthlene and tetrapropylnaphthlene (the weight ratio being1:1) having a boiling point range of 35040()C. and aniline pointof10.5C. and is hereinafter abbreviated as AX-2.

The rubber composition (Abbreviation: FAX-2) was prepared in a similarmanner to Example 1 in accordance with the white carbon compoundingformula shown in Table 5 below using the process oil (AX-2).

Compound 1 Compound ll (Comparative) (This Invention) Modulus at 300 7:elongation Kglcm 56 58 Tensile strength (Kg/Cm) 164 172 Elongation atbreak (7r) 550 570 Tear strength (Kg/cm) 46 54 Shore hardness v 48 4)Bound elasticity (25C.) 60 58 H-test (Kg/em) 12.5 13.8 (adhesion tonylon 1260 d/2) Contact staining property (Exposure to a weatherometerfor 48 hours at C.) none none EXAMPLE 2 40 TABLE 5-Continued Remarks:*Nonstaining styrenwbutadiene copolymer having styrene content of 23.5".

By way of comparison. comparative rubber compositions (Abbreviations:PA. PB and PD) were also prepared in a similar manner to the aboveformula, except that a commercially available, nonstaining. naphthenicoil (Abbrv. A for PA) or a commercially available. staining aromatic oil(Abbr. B for PB) was used as the process oil instead of FAX-2 as in thepresent invention. and no process oil was used (for PD).

vulcanization was conducted at C. for 40 minutes.

The resultant vulcanizates were subjected to accelerated weatheringtests with a weatherometer to determine discoloration degree.

The results are shown in Table 6 below.

Discolorati on degree by weatheromcter CXPOSUI'C1('% ComparativeThis-Inven "PA' PB 'PD FAX-2 Before exposure 83,0 83.0 84.5 85.0 Afterexposure 60.5 6510' magnesium oxide. of which whitenessdegree is 84.5%.

Degree of discoloration by oil shllt a 2 with a color meter to determinedegree of discoloration in a similar mannerto Example :2. Y

. Thezr-esults are shown in Table 9 below; by evaluating ,fromthe-viewpoint. of process oil bleed. 2, 1

TABLE 9 (71 weathcro meter CXPOSUI'C ICSI. J A I 1 PaAx-z PPA.. PPB PPD's'etsrg reassure so so so so The process oils of this invention and theoomparat. tives, the same as those used in Example 2, were compared witheach other with regard to discoloration by oil bleed.

First. orr p n ing l k rub r omp n (PPA. As is apparent from theresults, the rubber composiwere pr p r pecti ly m th tion of the presentinvention has a markedly superior process oils (A, B, AX-2) inaccordance with the comnonstaining property, as well as physicalproperties to pounding formula shown in Table 7 below. those of priorart rubber compositions.

Also, the black compound with no process oil was While the invention hasbeen described in detail and prepared (PPD). with reference to specificembodiments thereof. it will Further, a white rubber compound wasprepared acbe apparent to one skilled in the art that various cording tothe compounding formula as shown in Table changes and modifications canbe made therein with- 8 below (PW). out departing from the sprit andscope thereof.

Then the white compound in sheet form having a What is claimed is:thickness of ca.l mm was superimposed on each of the .30 1. A rubbercomposition containing therein 5-50 black compounds in sheet form andvulcanized at parts by weight per I00 parts by weight of a rubber 145C.for 40 minutes. component, of a nonstaining aromatic hydrocarbon oilThus, the corresponding composite vulcanizates which consistsessentially of polypropylnaphthalene of were obtained. the generalformula,

TABLE 7 Black Compound (parts by weight) PPA PPB PPD PPAX-Z SBR-l502 100I00 l00 100 FEF Carbon black 50 50 50 Zinc oxide 3.5 3.5 3.5 3.5 Stearicacid L5 L5 1.5 1.5 Antioxidant (WS) 10 1.0 1.0 1.0 Accelerator (CZ) 1.2L2 1.2 L2 9071 non-soluble sulfur 2.2 2.2 2.2 2.2 Picopale 100-SF 3.03.0 3.0 3.0 Process oil A B AX-2 TABLE 8 r g Rn White Compound (parts byweight) 35s No. l (NR) l0().0

inc oxide 7.0

Titanium Oxide (Tim white) 401) wherein R rs propyl group, n is aninteger of 2 to R Calcium carbonate (Hakuenka CC) 20.0 is a hydrogenatom or a methyl group and n is an integer of l and 2, the total numberof carbon atoms is the Microcystallinc w 5: alkyl side chains being sixto l3, and said oil having an Coumaron resin 20 Accelerator MSA L2aniline point of not more than 10 C and a boiling point non-solublesulfur 1.0 ranging from 280 to 450 C 65 2. A rubber composition asclaimed in claim 1,

Thereafter the vulcanized composite article irradiated by light on thewhite part thereof was measured wherein the amount of said nonstainingaromatic hydrocarbon oil is in a range of 10 to 25 parts by weight perparts by weight of the rubber component.

3. A rubber composition as claimed in claim I, wherein said anilinepoint is nottmore than C.

4. A rubber composition as claimed in claim I, wherein said aromatichydrocarbon oil has a boiling point in the range of 300-40()C.

5. A rubber composition as claimed in claim I. wherein saidpolypropylnaphthalene is tripropylnaphthalene.

6. A rubber composition as claimed in claim 5, wherein saidpolypropylnaphthalene is a mixture of triand tetrapropylnaphthalene.

7. A rubber composition as claimed in claim I, wherein the rubbercomponent is a high polarity rubber having high cohesive energy betweenmolecules selectcd from the group consisting of styrenebutadienecopolymer, butadiene-acrylonitrile copolymer, neoprene and blendsthereof with other polymers.

8. A rubber composition as claimed in claim 7, wherein the rubbercomponent is a styrene-butadiene copolymer or a blend thereof consistingof a major proportion of styrene-butadiene copolymer and a minorproportion of natural rubber.

9. A rubber composition as claimed in claim 1, which contains therein awhite reinforcing agent.

I0. A rubber composition as claimed in claim l, wherein saidpolypropylnaphthalene is obtained by treating naphthalene or anaphthalene fraction having a boiling point of 200 to 250C withpropylene.

II. A rubber composition as claimed in claim I. wherein said nonstainingaromatic hydrocarbon oil consists of said polypropylnaphthalene of saidgeneral formula.

1. A RUBBER COMPOSITION CONTAINING THEREIN 5-50 PARTS BY WEIGHT PER 100PARTS BY WEIGHTOF RUBBER COMPONENT, OF A NONSTANDING AROMATICHYDROCARBON OIL WHICH CONSISTS ESSENTIALLY OF POLYPROPYLINAPHTHALENE OFTHE GENERAL FORMULA,
 2. A rubber composition as claimed in claim 1,wherein the amount of said nonstaining aromatic hydrocarbon oil is in arange of 10 to 25 parts by weight per 100 parts by weight of the rubbercomponent.
 3. A rubber composition as claimed in claim 1, wherein saidaniline point is not more than -5*C.
 4. A rubber composition as claimedin claim 1, wherein said aromatic hydrocarbon oil has a boiling point inthe range of 300*-400*C.
 5. A rubber composition as claimed in claim 1,wherein said polypropylnaphthalene is tripropylnaphthalene.
 6. A rubbercomposition as claimed in claim 5, wherein said polypropylnaphthalene isa mixture of tri- and tetrapropylnaphthalene.
 7. A rubber composition asclaimed in claim 1, wherein the rubber component is a high polarityrubber having high cohesive energy between molecules selected from thegroup consisting of styrenebutadiene copolymer, butadiene-acrylonitrilecopolymer, neoprene and blends thereof with other polymers.
 8. A rubbercomposition as claimed in claim 7, wherein the rubber component is astyrene-butadiene copolymer or a blend thereof consisting of a majorproportion of styrene-butadiene copolymer and a minor proportion ofnatural rubber.
 9. A rubber composition as claimed in claim 1, whichcontains therein a white reinforcing agent.
 10. A rubber composition asclaimed in claim 1, wherein said polypropylnaphthalene is obtained bytreating naphthalene or a naphthalene fraction having a boiling point of200* to 250*C with propylene.
 11. A rubber composition as claimed inclaim 1, wherein said nonstaining aromatic hydrocarbon oil consists ofsaid polypropylnaphthalene of said general formula.